pvlib
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@@ -0,0 +1,181 @@
+"""
+Shaded fraction of a horizontal single-axis tracker
+====================================================
+
+This example illustrates how to calculate the 1D shaded fraction of three rows
+in a North-South horizontal single axis tracker (HSAT) configuration.
+"""
+
+# %%
+# :py:func:`pvlib.shading.shaded_fraction1d` exposes a useful method for the
+# calculation of the shaded fraction of the width of a solar collector. Here,
+# the width is defined as the dimension perpendicular to the axis of rotation.
+# This method for calculating the shaded fraction only requires minor
+# modifications to be applicable for fixed-tilt systems.
+#
+# It is highly recommended to read :py:func:`pvlib.shading.shaded_fraction1d`
+# documentation to understand the input parameters and the method's
+# capabilities. For more in-depth information, please see the journal paper
+# `10.1063/5.0202220 <https://doi.org/10.1063/5.0202220>`_ describing
+# the methodology.
+#
+# Let's start by obtaining the true-tracking angles for each of the rows and
+# limiting the angles to the range of -50 to 50 degrees. This decision is
+# done to create an example scenario with significant shading.
+#
+# Key functions used in this example are:
+#
+# 1. :py:func:`pvlib.tracking.singleaxis` to calculate the tracking angles.
+# 2. :py:func:`pvlib.shading.projected_solar_zenith_angle` to calculate the
+#    projected solar zenith angle.
+# 3. :py:func:`pvlib.shading.shaded_fraction1d` to calculate the shaded
+#    fractions.
+#
+# .. sectionauthor:: Echedey Luis <echelual (at) gmail.com>
+
+import pvlib
+
+import numpy as np
+import pandas as pd
+import matplotlib.pyplot as plt
+from matplotlib.dates import DateFormatter
+
+# Define the solar system parameters
+latitude, longitude = 28.51, -13.89
+altitude = pvlib.location.lookup_altitude(latitude, longitude)
+
+axis_tilt = 3  # degrees, positive is upwards in the axis_azimuth direction
+axis_azimuth = 180  # degrees, N-S tracking axis
+collector_width = 3.2  # m
+pitch = 4.15  # m
+gcr = collector_width / pitch
+cross_axis_slope = -5  # degrees
+surface_to_axis_offset = 0.07  # m
+
+# Generate a time range for the simulation
+times = pd.date_range(
+    start="2024-01-01T05",
+    end="2024-01-01T21",
+    freq="5min",
+    tz="Atlantic/Canary",
+)
+
+# Calculate the solar position
+solar_position = pvlib.solarposition.get_solarposition(
+    times, latitude, longitude, altitude
+)
+solar_azimuth = solar_position["azimuth"]
+solar_zenith = solar_position["apparent_zenith"]
+
+# Calculate the tracking angles
+rotation_angle = pvlib.tracking.singleaxis(
+    solar_zenith,
+    solar_azimuth,
+    axis_tilt,
+    axis_azimuth,
+    max_angle=(-50, 50),  # (min, max) degrees
+    backtrack=False,
+    gcr=gcr,
+    cross_axis_tilt=cross_axis_slope,
+)["tracker_theta"]
+
+# %%
+# Once the tracker angles have been obtained, the next step is to calculate
+# the shaded fraction. Special care must be taken
+# to ensure that the shaded or shading tracker roles are correctly assigned
+# depending on the solar position.
+# This means we will have a result for each row, ``eastmost_shaded_fraction``,
+# ``middle_shaded_fraction``, and ``westmost_shaded_fraction``.
+# Switching the parameters will be based on the
+# sign of :py:func:`pvlib.shading.projected_solar_zenith_angle`.
+#
+# The following code is verbose to make it easier to understand the process,
+# but with some effort you may be able to simplify it. This verbosity also
+# allows to change the premises easily per case, e.g., in case of a tracker
+# failure or with a different system configuration.
+
+psza = pvlib.shading.projected_solar_zenith_angle(
+    solar_zenith, solar_azimuth, axis_tilt, axis_azimuth
+)
+
+# Calculate the shaded fraction for the eastmost row
+eastmost_shaded_fraction = np.where(
+    psza < 0,
+    0,  # no shaded fraction in the morning
+    # shaded fraction in the evening
+    pvlib.shading.shaded_fraction1d(
+        solar_zenith,
+        solar_azimuth,
+        axis_azimuth,
+        shaded_row_rotation=rotation_angle,
+        axis_tilt=axis_tilt,
+        collector_width=collector_width,
+        pitch=pitch,
+        surface_to_axis_offset=surface_to_axis_offset,
+        cross_axis_slope=cross_axis_slope,
+        shading_row_rotation=rotation_angle,
+    ),
+)
+
+# Calculate the shaded fraction for the middle row
+middle_shaded_fraction = np.where(
+    psza < 0,
+    # shaded fraction in the morning
+    pvlib.shading.shaded_fraction1d(
+        solar_zenith,
+        solar_azimuth,
+        axis_azimuth,
+        shaded_row_rotation=rotation_angle,
+        axis_tilt=axis_tilt,
+        collector_width=collector_width,
+        pitch=pitch,
+        surface_to_axis_offset=surface_to_axis_offset,
+        cross_axis_slope=cross_axis_slope,
+        shading_row_rotation=rotation_angle,
+    ),
+    # shaded fraction in the evening
+    pvlib.shading.shaded_fraction1d(
+        solar_zenith,
+        solar_azimuth,
+        axis_azimuth,
+        shaded_row_rotation=rotation_angle,
+        axis_tilt=axis_tilt,
+        collector_width=collector_width,
+        pitch=pitch,
+        surface_to_axis_offset=surface_to_axis_offset,
+        cross_axis_slope=cross_axis_slope,
+        shading_row_rotation=rotation_angle,
+    ),
+)
+
+# Calculate the shaded fraction for the westmost row
+westmost_shaded_fraction = np.where(
+    psza < 0,
+    # shaded fraction in the morning
+    pvlib.shading.shaded_fraction1d(
+        solar_zenith,
+        solar_azimuth,
+        axis_azimuth,
+        shaded_row_rotation=rotation_angle,
+        axis_tilt=axis_tilt,
+        collector_width=collector_width,
+        pitch=pitch,
+        surface_to_axis_offset=surface_to_axis_offset,
+        cross_axis_slope=cross_axis_slope,
+        shading_row_rotation=rotation_angle,
+    ),
+    0,  # no shaded fraction in the evening
+)
+
+# %%
+# Plot the shaded fraction result for each row:
+plt.plot(times, eastmost_shaded_fraction, label="East-most", color="blue")
+plt.plot(times, middle_shaded_fraction, label="Middle", color="green",
+         linewidth=3, linestyle="--")  # fmt: skip
+plt.plot(times, westmost_shaded_fraction, label="West-most", color="red")
+plt.title(r"$shaded\_fraction1d$ of each row vs time")
+plt.xlabel("Time")
+plt.gca().xaxis.set_major_formatter(DateFormatter("%H:%M"))
+plt.ylabel("Shaded Fraction")
+plt.legend()
+plt.show()
@@ -11,3 +11,5 @@ Shading
    shading.masking_angle_passias
    shading.sky_diffuse_passias
    shading.projected_solar_zenith_angle
+   shading.shaded_fraction1d
+   
@@ -15,6 +15,10 @@ Deprecations
 
 Enhancements
 ~~~~~~~~~~~~
+* Add function :py:func:`pvlib.shading.shaded_fraction1d`, to calculate the
+  shade perpendicular to ``axis_azimuth``. The function is applicable to both
+  fixed-tilt and one-axis tracking systems.
+  (:issue:`1689`, :pull:`1725`, :pull:`1962`)
 
 
 Bug fixes
@@ -36,4 +40,5 @@ Requirements
 Contributors
 ~~~~~~~~~~~~
 * Cliff Hansen (:ghuser:`cwhanse`)
-* Siddharth Kaul (:ghuser:`k10blogger`)
+* Mark Mikofski (:ghuser:`mikofski`)
+* Siddharth Kaul (:ghuser:`k10blogger`)